1. Field of the Invention
The present invention relates to a terminal seat, and in particular to a quick-detachable terminal seat and a programmable logic controller having the same.
2. Description of Prior Art
A terminal seat is a common part in an electronic apparatus. For example, a programmable logic controller (PLC) commonly used in industrial automation is provided with a terminal seat whose surface is arranged with several rows of terminals. A portion of terminals is electrically connected to a circuit board of the PLC, while the other portion of terminals is electrically connected to other electronic elements (such as sensors or controllers) via leads. Finally, the terminal seat is locked to a casing of the PLC. For example, in case of a switchboard on a large-sized electronic apparatus, a plurality of terminal seats is arranged side by side on the switchboard. Since the distance between these terminals is so close that the space available for arranging leads becomes narrow. Even, an operator for arranging the leads may touch the terminals carelessly and thus get an electric shock.
In view of the above, the industry in this art develops a detachable terminal seat, whereby the operator can connect a plurality of leads to the predetermined terminals in advance. Then, the whole detachable terminal seat is electrically connected to the circuit board and fixed to the switchboard. In this way, the problem of narrow space and the risk of getting an electric shock can be avoided.
However, in practice, such a detachable terminal seat still has drawbacks as follows. First, since most of the detachable terminal seats are fixed to the switchboard via screws, the operator needs to use an additional tool (such as a screw driver) to loosen the screws in order to detach the terminal seat from the switchboard. As a result, during the detachment of the terminal seat, the problem of narrow space and the risk of getting an electric shock still exist. Some detachable terminal seats are fixed to the switchboard via fasteners or plastic knobs. Although such an arrangement allows the operator not to use a tool, the operator still needs to hold the terminal seat by one hand, loosen the fastener or plastic knob by the other hand, and then pull the terminal seat out of the switchboard with labor. When a plurality of detachable terminal seats is arranged side by side with the top surfaces of two adjacent terminal seats being in flush with each other, it is difficult for the operator to find a point on the aligned surfaces for exerting a force to pull the terminal seat out of the switchboard.
In prior art, another kind of detachable terminal seat is developed, in which a pull rod is provided. This pull rod functions as an insertion pin for inserting into the terminal seat to thereby fix the rear end of the terminal seat to a casing. However, such a pull rod cannot lift up the terminal seat. Thus, when the operator intends to pull the terminal seat out of the switchboard, the operator has to pull the pull rod out of the terminal seat, and then pull the terminal seat out of the casing. Therefore, the problem of narrow space and difficulty in finding a point for exerting forces still exist.
In the conventional detachable terminal seat, not only its fixation to the casing is defective, but also the operator needs to exert a larger force to detach the terminal seat from the circuit board. On the other hand, the operator has to align the terminal seat with the circuit board, and then press the terminal seat into the casing to complete the assembly. Thus, if a labor-saving mechanism could be provided in the conventional detachable terminal seat, the detachment of the terminal seat may become easier.
Therefore, it is an important issue for the present inventor to solve the above problems.